What is the atomic Radius?

Let’s comment on the an interpretation of the atom radius, also called atom size, and the atomic radius trend on the routine table. The atomic radius is measure as fifty percent the distance between two nuclei the the exact same atoms that are bonded together. While her initial assumed may have actually been to measure the distance from the center of one atom’s nucleus to the leaf of that is electron cloud, this is inaccurate and also not feasible. This is because the borders of orbitals are fairly fuzzy, and they also change under different conditions. Therefore the atom radius is measured as shown in the diagram below.

You are watching: Which element has the largest atomic radius


Atomic Radius trend on the periodic Table


Atomic radii boost toward the bottom left edge of the periodic table, through Francium having the biggest atomic radius. Atom decrease in size across the duration and increase in size down the group. Let’s failure the trend right into its period and team trends.

Period Trends

There are countless trends top top the regular table. Because that example, ionization energy, electronegativity, and also of food atomic radius which us will talk about now. Throughout a period, atom radii decrease. This is since while the number of electrons rises down the period, they only add to the very same main energy level, and therefore perform not expand the electron cloud. Down the period, however, the number of protons also increases. This enhanced positive charge attracts or pulls, the electron in closer come the nucleus, diminish the atomic radius.


One thing to note is that the impact of the attraction between the positively charged nucleus and the electron is slightly countered by the repulsion the electrons together they room successively added. This is why the difference in atomic radii decreases down each period.

Group Trend

Down a group, atom radii increase. This is because between every group, electrons occupy successively greater energy levels. As electron cloud size increase, so do atomic radii.


The tendency on a Graph

As shown in the graph below, the atomic radius is largest at the very first element in every period, and it decreases down each period.

See more: How Much Can Brock Lesnar Bench Press, Brock Lesnar Can Bench Press Over 600 Pounds


Smallest and also Largest atom Radius

Francium has actually the biggest atomic dimension on the regular table, and helium has actually the smallest atomic size.